The damascene method is sometimes used in situations when copper (Cu) wires are formed in wire trenches or via holes formed in interlayer insulation film. In order to prevent metallic diffusion, in the damascene method, a diffusion barrier film (barrier metal) is formed in the inner wall of the wire trenches or in the inner wall of the via holes before the metal wires are formed.
Refractory metals such as tantalum (Ta) or titanium (Ti), or nitride compounds of these metals are used as materials of the diffusion barrier film. However, these metallic films have high resistance, thereby causing increased resistance in metal wires and increased RC delay. Thus, as the shrinkage of metal wires has progressed in recent years, there is a trend towards thinner films being used for the diffusion barrier film.
On the other hand, with the objective of avoiding RC delay, there are cases where porous low-dielectric constant material is used as the material in the interlayer insulation film, for example. Porous low-dielectric constant material is easily damaged by plasma during the manufacturing process. The damaged film is more likely to absorb moisture on its surface or in its interior. Thus, the diffusion barrier film which is formed on such a low-dielectric constant material is easily oxidized or altered by the moisture released from the interlayer insulation film, thereby suffering degraded barrier capabilities.
In Japanese Unexamined Patent Application Publication No. 2005-277390, a technology using copper-manganese (CuMn) seed layers as material in diffusion barrier film is disclosed. In this method, a copper-manganese film is directly formed on the interlayer insulation film as the seed film for the plating of copper wires. According to this method, the manganese in the copper-manganese film reacts with the silicon and oxygen included in the interlayer insulation film, forming a 2 to 3 nm self-aligned MnOXSiY layer at the boundary between the interlayer insulation film and the copper wires. The MnOXSiY layer formed therein functions as an diffusion barrier film, thereby securing the barrier capabilities of copper wires in relation to the interlayer insulation film without using tantalum (Ta) or titanium (Ti) used in conventional diffusion barrier films.
However, in a manufacturing process using a copper-manganese film, a problem occurs in which favorable adhesion between the MnOXSiY layer and the interlayer insulation film cannot be achieved. Consequently, if a heat treatment is performed after the copper wires are formed for example, there are cases where the copper wires formed in the wire trenches or via holes move upward (siphon phenomenon). Additionally, there are cases where copper wires peel off during CMP (Chemical Mechanical Polish) process. As a result, a problem occurred in which separation occurred between the copper wires and the underlying wires formed under the copper wires and the yield of the semiconductor apparatus worsened.
Thus, the productivity of a semiconductor apparatus is not improved when an diffusion barrier film or copper-manganese seed layer is formed on an interlayer insulation film according to a conventional manufacturing process before copper wires are formed in the interlayer insulation film.